Mazosia byssoidea Lebreton & Ertz, 2024

Ertz, Damien & Lebreton, Élise, 2024, A new corticolous species of Mazosia A. Massal. (Roccellaceae, Arthoniales) from Guadeloupe, remarkable by its byssoid thallus, Cryptogamie, Mycologie 20 (1), pp. 1-10 : 4-8

Mazosia byssoidea Lebreton & Ertz , sp. nov.

( Fig. 4 )

Differing from all species of Mazosia by the combination of a distinct byssoid thallus, 1-septate ascospores, stipitate pycnidia and by the production of roccellic acid as a major secondary metabolite.

HOLOTYPE. — Guadeloupe. Sainte-Rose municipality, forest managed by the Office national des forêts, hiking trail from Sofaïa to Saut des Trois Cornes, on the banks of the moustique river, 16°17’9.179”N, 61°43’34.374”W, 200-300 m elevation, riparian tropical rainforest, on tree, 03.IV.2023, Elise Lebreton 2311 (holo-, PC[PC0779827 ]; GenBank [ OR733354 , OR725979 , OR725977 ]).

ISOTYPE. — Guadeloupe. Sainte-Rose municipality, forest managed by the Office national des forêts, hiking trail from Sofaïa to Saut des Trois Cornes, on the banks of the moustique river, 16°17’9.179”N, 61°43’34.374”W, 200-300 m elevation, riparian tropical rainforest, on tree, 03.IV.2023, Elise Lebreton 2311 (iso-, BR [ BR 5030170788830]).

PARATYPE. — Guadeloupe. Sainte-Rose municipality, forest managed by the Office national des forêts, hiking trail from Sofaïa to Saut des Trois Cornes, 16°17’13.463”N, 61°43’33.146”W, 200-300 m elevation, dense tropical rainforest, on tree, 03.IV.2023, Elise Lebreton 2310 (para-, GUAD, LG[PSA10A-18060]; GenBank [OR733353, OR725976]); ibid., 29.I.2022, Elise Lebreton 1618 (para-, GUAD, LG[IMV00A-14517]).

ETYMOLOGY. — The epithet is derived from the structure of the thallus that is distinctly byssoid.

CHEMISTRY. — Thallus surface, medulla and lower side of thallus and pycnidia K–, C–, KC–, PD–, UV–. TLC (solvent A): roccellic acid (major) (specimens Lebreton 2310 and Lebreton 2311 tested).

DISTRIBUTION AND ECOLOGY. — So far known only from Guadeloupe (Basse-Terre island) in the Lesser Antilles, where it inhabits a dense humid forest or riparian forest managed by the Office national des forêts. It is only known from two large trees. The holotype (Lebreton 2311) was found on the riverbank, on a tree that was sparsely colonized by the lichen. The paratypes (Lebreton 1618, Lebreton 2310) were collected on the second tree, in 2022 and 2023 respectively ( Fig. 1 ). This tree was on the hiking trail and the trunk was abundantly covered with M. byssoidea Lebreton & Ertz , sp. nov. but only a few thalli had apothecia. Mazosia byssoidea Lebreton & Ertz , sp. nov. is clearly rare and the current populations should be protected and monitored in the future. The locality is not included in the National Park and should therefore be included in a natural reserve. The species should be searched for elsewhere in Guadeloupe and the Caribbean islands to better access its conservation status.

MYCOBANK. — MB850668.

DESCRIPTION

Thallus up to c. 5 cm in diam., loosely attached to the substrate, byssoid, smooth, rarely sparsely squamulose, effuse, pale olive-grey, matt, ecorticate, esorediate, heteromerous, c. 150 µm thick. Prothallus poorly differentiated, byssoid, white to dark brownish, sometimes white with a dark brownish margin.Photobiont layer forming the upper part of the thallus; photobiont trentepohlioid, in chains, formed of rounded to elongate, 9-22×8-15 µm cells. Medulla thick, white, I+ pale orange, KI+ pale orange, formed of 2-3 µm wide hyphae, with numerous crystals of calcium oxalate (H2SO4), 1-7(-10) µm diam. Hypothallus loosely byssoid, thin and discontinuous, dark brown to blackish, formed of (2.5-)3-4 µm wide dark brown hyphae; hypothallus free areas on the lower thallus surface whitish, rarely pale cream. Ascomata apothecioid, sessile, often distinctly constricted at the base, rounded, single, not forming stromatic aggregates, sparsely distributed on the thallus, 0.33-0.85 mm diam. (n = 24); margin prominent, of the same colour of the thallus, smooth, (90-)150-210 µm thick, epruinose; hymenial disc black, covered by a very thin layer of whitish hairs; hairs straight, vertical, c. 10-13 ×2-3 µm. Excipulum inconspicuous. Hymenium clear, hyaline to pale fawn, 60-90 µm tall, I+ pale reddish brown, KI+ pale blue; epihymenium pale brown to orange, K–, I+ pale reddish brown, KI+ pale blue. Paraphysoids branched-anastomosing, c. 2 µm

thick, often slightly enlarged in epihymenium (c. 3 µm) and forming straight hyaline hairs on the surface of the hymenial disc. Hypothecium dark brown, thick, not extending to the substrate, 75-100 µm thick, I–, K+ olivaceous. Ascus 8-spored, narrowly clavate, 54-65 × 12-15 µm (n =5), with a tiny but often poorly developed ocular chamber; endoascus I+ reddish, KI+ pale blue with a KI+ dark blue apical ring. Ascospores hyaline, ±fusiform or narrowly ovoid, with the upper half often slightly wider, 1-septate, not constricted at the septum, with the cells equal or one slightly longer, I+ pale yellowish, (13-)13.6-16.6(-19) × (4-)4.2-5(-5) µm (n = 25); gelatinous sheath sometimes visible, c. 0.5-0.8 µm thick. Pycnidia single, very rarely grouped by two, sparsely distributed on the thallus, straight, stipitate, cylindrical or slightly wider at the base or at the half upper part, not or slightly constricted at the base, unbranched, whitish or of the same colour as the thallus except for the top that is pale greyish and with the ostiole visible as a tiny black dot, epruinose, (0.39-)0.45- 0.75(-0.89) × (0.19-)0.23-0.3(-0.33) mm (n = 24); wall in section pale brown to orange, K+ olivaceous, surrounded by a thick white medulla layer with trentepohlioid photobiont present near the surface; conidiogenous cells unbranched, straight, hyaline, 6-8×2-2.5 µm; conidia hyaline, non-septate, fusiform-ellipsoid, 5.5-7×2.5-3 µm (n =20).

NOTES

The new species is unique within the genus Mazosia by its byssoid thallus. All other species in the genus have a compact thallus. Some species produce a pilose thallus such as Mazosia pilosa Kalb &Vězda and M. weii Z.T. Yao, S.H.Jiang & Z.F.Jia , or a tomentum such as M. tomentifera Vězda & Lumbsch (see Yao et al. 2021b for a key to species of Mazosia with pilose thalli). These hairs like structures are developed from compact

thalli, which are very different from the loosely arranged filamentous structure of a byssoid thallus. All these pilose species also differ notably by their foliicolous habit and usually more septate ascospores ( Kalb & Vězda 1988; Lumbsch & Vězda 1990; Lücking 2006; Yao et al. 2021b). Besides M. byssoidea Lebreton & Ertz , sp. nov., only two other species of Mazosia produce 1-septate mature ascospores: the lichenized M. uniseptata Lücking and the lichenicolous M. adelphoparasitica , which both are species confined to leaves of vascular plants ( Matzer 1996; Lücking 2006).

Mazosia byssoidea Lebreton & Ertz , sp. nov. differs from other taxa of Roccellaceae having a byssoid thalli by the combination of apothecioid ascomata not forming stromatic structures, 1-septate ascospores, stipitate pycnidia and a chemistry with roccellic acid.Among the byssoid Roccellaceae , the new species is most similar to the genus Tania Egea, Torrente & Sipman , but species of this genus differ by a chemistry with schizopeltic acid and by 3-5-septate ascospores ( Egea et al. 1995; Harada & Yamamoto 2006). Species of the genus Sagenidiopsis R.W.Rogers & Hafellner differ by 3-septate ascospores, different secondary metabolites (e.g. Rogers & Hafellner 1987; Egea et al. 1995) and only a distantly phylogenetic position ( Fig. 2 ). Species of the genera Dichosporidium and Streimannia G.Thor differ by perithecioid ascomata aggregated in stromalike structures ( Thor 1990; Egea et al. 1995).

The new species is also reminiscent of the monotypic genus Catarraphia A.Massal. that also has a thallus loosely attached to the substrate and apothecioid ascomata. However, Catarraphia differs from the new species by a corticate thallus; ascomata entirely (including margins) covered by a whitish or bluish pruina; an excipulum made of hyaline hyphae that are densely aggregated, arranged in an anticlinal manner and completely masked by brown granules that dissolve in K; paraphysoids that are gelatinized in the lower half; 3(-4)-septate ascospores having mucilaginous attenuated appendages at both ends; and a more complex chemistry with cyclographin ( Elix et al. 1995) and several unidentified substances that are visible under UV light on the TLC plates and show a light yellow color after developing with sulfuric acid ( Egea & Torrente 1993; Egea et al. 1996). Moreover, its single species, C. dictyoplaca (Mont. & Bosch) A.Massal. , is only known from the eastern Paleotropics and Melanesia ( Egea et al. 1996).

Because the thallus is unusual for a species of Mazosia and reminiscent of the thalli of some Arthoniales growing in Guadeloupe such as Dichosporidium nigrocinctum (Ehrenb.) G.Thor , we wondered whether the ascomata of the new species might represent a lichenicolous fungus growing on the thallus of a second sterile species, in particular as a lichenicolous species ( M. adelphoparasitica ) is already known in the genus. In order to test this hypothesis, some of the sequences used in this study were produced by direct PCRs using a few thallus hyphae only taken far from the ascomata (see Methods). These sequences supported a placement in Mazosia . Moreover, no necrotic areas were observed around the ascomata and the chemistry of the thallus is different from D. nigrocinctum that always produces protocetraric acid and pycnidia that are not stipitate ( Thor 1990). For these reasons, we are convinced that the new species is a lichenized Mazosia .

Figures

FIG. 4. — Mazosia byssoidea Lebreton & Ertz, sp. nov. (A, B, F, H-J, Lebreton 2311; C-E, G, K, Lebreton 2310): A, B, thallus and apothecia; C, thallus with pycnidia; D, prothallus; E, one pycnidium; F, section of one apothecium in water; G, lower side of the thallus; H, ascus in KI; I, ascospores in water; J, ascospores in KI; K, conidia in water. Scale bars: A, C, 1 mm; B, D, G, 500 µm; E, 250 µm; F, 100 µm; H-K, 5 µm.

FIG. 1. — Trunk with Mazosia byssoidea Lebreton & Ertz, sp. nov. in its type locality in Guadeloupe.Knife marks on bark correspond to paratypes sampling (Lebreton 1618, Lebreton 2310).

FIG. 2. — Phylogeny of Roccellaceae Chevall. based on a dataset of RPB2 sequences that resulted from a RAxML analysis. Maximum likelihood bootstrap values, when significant (≥ 70), are shown near internal branches. Internal branches considered as strongly supported are represented by thicker lines. The newly sequenced samples are in bold and their names are followed by collection numbers,which act as specimen and sequence identifiers.The lineage corresponding to the new species is in a blue rectangle.